Survival of Listeria monocytogenes on the Surface of Egg Shells and During Frying of Whole and Scrambled Eggs

1992 ◽  
Vol 55 (11) ◽  
pp. 862-865 ◽  
Author(s):  
R. E. BRACKETT ◽  
L. R. BEUCHAT
Keyword(s):  
Listeria Monocytogenes ◽  
Storage Period ◽  
High Population ◽  
Log10 Reduction ◽  
Internal Temperature ◽  
Shell Eggs ◽  
Wash Buffer ◽  
Tryptose Phosphate Broth ◽  
Egg Shells

Studies were done to determine the survival characteristics of Listeria monocytogenes on shell eggs and after cooking raw whole and scrambled eggs by frying. Samples were inoculated with low or high populations of a five-strain mixture of L. monocytogenes. Survival of the organism on shells of unbroken eggs was monitored over a 6-week storage period at 5 and 20°C. The presence of L. monocytogenes was determined by subjecting egg samples to primary enrichment in tryptose phosphate broth followed by plating the broth on Lee Modified Oxford agar. Enumeration was done by directly plating serially diluted wash buffer from shell eggs and diluted fried eggs directly on Lee Modified Oxford agar. Both low (102 CFU per egg) and high (104 CFU per egg) populations of L. monocytogenes on the surface of egg shells decreased to <10 CFU per egg after 6 d of storage at 5 and 20°C. Frying whole eggs “sunnyside up” until albumen was partially coagulated reduced both low (102 CFU/g) and high (105 CFU/g) populations of L. monocytogenes by only 0.4 log10 CFU/g. In contrast, frying one or three scrambled eggs to an internal temperature of 70–73°C reduced low (102 CFU/g) populations of L. monocytogenes to undetectable and <102 CFU/g, respectively. Frying three scrambled eggs containing high (105 CFU/g) populations caused a 3 log10 reduction. Frying one scrambled egg containing a high population resulted in <102 CFU/g. Both low (104 CFU/g) and high (107 CFU/g) populations of L. monocytogenes remained unchanged or decreased slightly when raw slightly beaten whole eggs were allowed to stand for up to 3 h at 20°C.

Inhibition of Listeria monocytogenes in Turkey and Pork-Beef Bologna by Combinations of Sorbate, Benzoate, and Propionate

2007 ◽  
Vol 70 (1) ◽  
pp. 214-217 ◽  
Author(s):  
KATHLEEN GLASS ◽  
DAWN PRESTON ◽  
JEFFREY VEESENMEYER
Keyword(s):  
Growth Rate ◽  
Listeria Monocytogenes ◽  
Sodium Benzoate ◽  
Antimicrobial Agents ◽  
Storage Period ◽  
Potassium Sorbate ◽  
Internal Temperature ◽  
High Moisture ◽  
Sodium Propionate ◽  
Low Concentrations

The control of Listeria monocytogenes was evaluated with ready-to-eat uncured turkey and cured pork-beef bologna with combinations of benzoate, propionate, and sorbate. Three treatments of each product type were formulated to include control with no antimycotic agents; a combination of 0.05% sodium benzoate and 0.05% sodium propionate; and a combination of 0.05% sodium benzoate and 0.05% potassium sorbate. Ingredients were mixed, stuffed into fibrous, moisture-impermeable casings, cooked to an internal temperature of 73.9°C, chilled, and sliced. The final product was surface inoculated with L. monocytogenes (4 log CFU per package), vacuum packaged, and stored at 4°C for 13 weeks. The antimycotic addition to the second and third uncured turkey treatments initially slowed the pathogen growth rate compared with the control, but populations of L. monocytogenes increased 5 log or more by 6 weeks. In contrast, the addition of antimycotic combinations in the cured bologna prevented growth of L. monocytogenes during the 13-week storage period at 4°C, compared with a more than 3.5-log increase in listerial populations in the control bologna, to which no antimicrobial agents had been added. These data suggest that low concentrations of antimycotic agents can prevent L. monocytogenes growth in certain ready-to-eat meats. Additional research is needed to define the levels needed to prevent growth of L. monocytogenes in high-moisture cured and uncured ready-to-eat meat and poultry and for gaining governmental approval for their use in such formulations.

Inactivation of Listeria monocytogenes on Hot-smoked Salmon by the Interaction of Heat and Smoke or Liquid Smoke†

1997 ◽  
Vol 60 (6) ◽  
pp. 649-654 ◽  
Author(s):  
FRANK T. POYSKY ◽  
ROHINEE N. PARANJPYE ◽  
MARK E. PETERSON ◽  
GRETCHEN A. PELROY ◽  
ANNE E. GUTTMAN ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Minimum Temperature ◽  
Soluble Fraction ◽  
Internal Temperature ◽  
Lethal Temperature ◽  
Entire Process ◽  
Smoked Fish ◽  
Liquid Smoke ◽  
Full Strength ◽  
Smoked Salmon

L. monocytogenes was inoculated onto the surface of brined salmon steaks and heat processed in a commercial smokehouse to simulate a hot process for preparing smoked fish. The minimum temperature required for inactivation of L. monocytogenes was 153°F (67.2°C) when generated smoke was applied throughout the entire process. When generated smoke was added only during the last half of the process, L. monocytogenes was recovered from steaks heated to temperatures as high as 176°F (80.0°C). When smoke was not applied during the process, L. monocytogenes survived on steaks heated to internal temperatures between 131°F and 181°F (55.0 to 82.8°C) but was not isolated from steaks heated above 181°F (82.8°C). When liquid smoke CharSol C-l0 was applied as a full-strength (100%) dip before processing, L. monocytogenes was inactivated in samples processed at temperatures as low as 138°F (58.9°C). When liquid smoke l0-Poly or CharSol C-l0 was applied at a concentration of 50%, the lethal temperature was increased to the range of 145 to 150°F (62.8 to 65.6°C). With further dilution of C-l0 to 25% and 10% the inactivation temperatures increased to 156°F (68.9°C) and 163°F (72.8°C). A full-strength dip of CharOil, the oil-soluble fraction of CharSol C-l0, was less effective, and L. monocytogenes survived in salmon steaks processed to an internal temperature of 166°F (74.4°C), the highest temperature tested with this liquid smoke. This study provides evidence that heat alone is not reliable for inactivation of L. monocytogenes during the hot-smoking process. The proper stage and duration of smoke application or proper composition and concentration of liquid smoke in combination with heat are critical for inactivation of the organism.

Salmonella prevalence in commercial raw shell eggs in Japan: a survey

2010 ◽  
Vol 139 (7) ◽  
pp. 1060-1064 ◽  
Author(s):  
Y. SASAKI ◽  
Y. TSUJIYAMA ◽  
T. ASAI ◽  
Y. NODA ◽  
S. KATAYAMA ◽  
...  
Keyword(s):  
Control Measures ◽  
Retail Stores ◽  
Potential Hazard ◽  
Shell Eggs ◽  
Hygienic Practice ◽  
Egg Shells ◽  
Chicken Eggs

SUMMARYWe examined 20 300 raw shell chicken eggs sold at retail stores in Japan for Salmonella outside and inside eggs. The eggs were purchased at 220 retail stores throughout Japan between August 2007 and January 2008. Of 2030 pooled egg samples (10 eggs/sample), Salmonella was isolated from five shell samples (0·25%), but not from any of egg-content samples. The serovars of the isolates were Salmonella Enteritidis (2), S. Derby, S. Livingstone and S. Cerro. The samples positive for Salmonella originated from five different egg grading and packaging (GP) centres. All the GP centres washed their egg shells according to government guidelines for hygienic practice in GP centres. Thus, practical control measures at GP centres need to be reviewed and implemented to diminish Salmonella prevalence of egg shells because Salmonella contamination on eggs is a potential hazard for foodborne salmonellosis in Japan.

Effects of Irradiation on Bacterial Load and Listeria monocytogenes in Raw Chicken

1992 ◽  
Vol 55 (5) ◽  
pp. 389-391 ◽  
Author(s):  
YURI VARABIOFF ◽  
GREGORY E. MITCHELL ◽  
STEPHEN M. NOTTINGHAM
Keyword(s):  
Listeria Monocytogenes ◽  
Cold Storage ◽  
Bacterial Load ◽  
Storage Period ◽  
Plate Count ◽  
Standard Plate Count ◽  
Standard Plate ◽  
Effects Of Irradiation On

After irradiation of chickens to a dose of 2.5 kGy, the decrease in the standard plate count (SPC) was similar in air and in vacuum-packaged chickens. During storage at 4°C for 15 d, the SPC increased progressively in both types of packaged chickens. At the end of the storage period, the SPC was higher in air-packaged chicken than in vacuum-packaged chickens. In irradiated chickens, Listeria monocytogenes was only recovered from the vacuum-packaged chickens after 7 d cold storage. In unirradiated chickens, L. monocytogenes proliferated similarly in both air- and vacuum-packaged chickens.

Changes in Populations of Listeria monocytogenes Inoculated on Packaged Fresh-Cut Vegetables

1998 ◽  
Vol 61 (2) ◽  
pp. 192-195 ◽  
Author(s):  
J. M. FARBER ◽  
S. L. WANG ◽  
Y. CAI ◽  
S. ZHANG
Keyword(s):  
Listeria Monocytogenes ◽  
Extreme Temperature ◽  
Storage Period ◽  
Population Increase ◽  
Good Growth ◽  
Cell Numbers ◽  
Unit Increase ◽  
Fresh Cut ◽  
Subsequent Storage ◽  
Mix Temperature

A variety of Wholesale and retail packaged vegetables and salads were inoculated with a mixture of strains of Listeria monocytogenes and incubated at 4 and 10°C. Whole rutabagas, butternut squash, and onions, as well as packaged Caesar salad, carrots, coleslaw mix, and stir-fry vegetables were purchased from local supermarkets in the Ottawa area. L. monocytogenes population levels remained constant on all fresh-cut vegetables stored at 4°C for 9 days, except for carrots and butternut squash: counts of cell numbers declined on carrots and increased on the butternut squash. Fresh-cut vegetables stored at 10°C, however, supported good growth of L. monocytogenes on all vegetables tested, except for chopped carrots, where the population decreased approximately 2 log units over a 9-day storage period. As in the situation with the produce stored at 4°C, butternut squash supported the highest rate of cell growth. In addition, Caesar salad and coleslaw mix were kept at 25°C for 1 or 2 days before subsequent storage at 4 or 10°C to simulate extreme temperature-abuse conditions. In Caesar salad stored at 4°C, by day 6 an initial 24- and 48-h temperature abuse at 25°C led to a 1.21- and 2.55-log-unit population increase, respectively, over the control. Similar increases were observed on Caesar salads stored at 10°C. Compared to Caesar salad, coleslaw mix temperature-abused at 25°C and then stored at 4°C supported slightly greater increases in the population of L. monocytogenes, i.e., a 3.22- and 3.83-log-unit increase over the control for the 1- and 2-day abused samples, respectively. Coleslaw mix samples temperature-abused and then stored at 10°C, however, only showed log unit increases of 1.75 and 1.94, respectively, compared to the Controls. These results point to the importance of strict temperature control to prevent or reduce the growth of L. monocytogenes cells on fresh-cut vegetables.

Growth and thermal inactivation of Listeria monocytogenes in cabbage and cabbage juice

1986 ◽  
Vol 32 (10) ◽  
pp. 791-795 ◽  
Author(s):  
L. R. Beuchat ◽  
R. E. Brackett ◽  
D. Y.-Y. Hao ◽  
D. E. Conner
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Inactivation ◽  
Storage Period ◽  
Viable Population ◽  
Effects Of Ph ◽  
Increased Sensitivity ◽  
Stressed Cells ◽  
Heat Pasteurization ◽  
Recovery Medium ◽  
Heating Medium

Studies were done to determine the interacting effects of pH, NaCl, temperature, and time on growth, survival, and death of two strains of Listeria monocytogenes. Viable population of the organism steadily declined in heat-sterilized cabbage stored at 5 °C for 42 days. In contrast, the organism grew on raw cabbage during the first 25 days of a 64-day storage period at 5 °C. Growth was observed in heat-sterilized unclarified cabbage juice containing ≤5% NaCl and tryptic phosphate broth containing ≤10% NaCl. Rates of thermal inactivation increased as pH of clarified cabbage juice heating medium was decreased from 5.6 to 4.0. At 58 °C (pH 5.6), 4 × 106 cells/mL were reduced to undetectable levels within 10 min. Thermal inactivation rates in clarified cabbage juice (pH 5.6) were not significantly influenced by the presence of up to 2% NaCl; however, heat-stressed cells had increased sensitivity to NaCl in tryptic soy agar recovery medium. Cold enrichment of heat-stressed cells at 5 °C for 21 days enhanced resuscitation. Results indicate that L. monocytogenes can proliferate on refrigerated (5 °C) raw cabbage which, in turn, may represent a hazard to health of the consumer. Heat pasteurization treatments normally given to cabbage juice or sauerkraut would be expected to kill any L. monocytogenes cells which may be present.

scholarly journals Survival and Heat Resistance of Listeria monocytogenes after Exposure to Alkali and Chlorine

2001 ◽  
Vol 67 (6) ◽  
pp. 2555-2563 ◽  
Author(s):  
P. J. Taormina ◽  
L. R. Beuchat
Keyword(s):  
Listeria Monocytogenes ◽  
Thermal Processing ◽  
Food Service ◽  
Potassium Phosphate ◽  
Lethal Effect ◽  
Free Chlorine ◽  
Processing Plant ◽  
Alkaline Stress ◽  
Tryptose Phosphate Broth ◽  
D Values

ABSTRACT A strain of Listeria monocytogenes isolated from a drain in a food-processing plant was demonstrated, by determination of D values, to be more resistant to the lethal effect of heat at 56 or 59°C following incubation for 45 min in tryptose phosphate broth (TPB) at pH 12.0 than to that of incubation for the same time in TPB at pH 7.3. Cells survived for at least 6 days when they were suspended in TPB at pHs 9.0, 10.0, and 11.0 and stored at 4 or 21°C. Cells ofL. monocytogenes incubated at 37°C for 45 min and then stored for 48 or 144 h in TPB at pH 10.0 were more resistant to heat treatment at 56°C than were cells stored in TPB at pH 7.3. The alkaline-stress response in L. monocytogenes may induce resistance to otherwise lethal thermal-processing conditions. Treatment of cells in 0.05 M potassium phosphate buffer (pH 7.00 ± 0.05) containing 2.0 or 2.4 mg of free chlorine per liter reduced populations by as much as 1.3 log10 CFU/ml, while treatment with 6.0 mg of free chlorine per liter reduced populations by as much as 4.02 log10 CFU/ml. Remaining subpopulations of chlorine-treated cells exhibited some injury, and cells treated with chlorine for 10 min were more sensitive to heating at 56°C than cells treated for 5 min. Contamination of foods by L. monocytogenes cells that have survived exposure to processing environments ineffectively cleaned or sanitized with alkaline detergents or disinfectants may have more severe implications than previously recognized. Alkaline-pH-induced cross-protection of L. monocytogenes against heat has the potential to enhance survival in minimally processed as well as in heat-and-serve foods and in foods on holding tables, in food service facilities, and in the home. Cells surviving exposure to chlorine, in contrast, are more sensitive to heat; thus, the effectiveness of thermal processing in achieving desired log10-unit reductions is not compromised in these cells.

Survival and Growth of Listeria monocytogenes and Enterohemorrhagic Escherichia coli O157:H7 in Minimally Processed Artichokes

2003 ◽  
Vol 66 (12) ◽  
pp. 2203-2209 ◽  
Author(s):  
SUSANA SANZ ◽  
MERCEDES GIMÉNEZ ◽  
CARMEN OLARTE
Keyword(s):  
Escherichia Coli ◽  
Listeria Monocytogenes ◽  
Tap Water ◽  
Storage Period ◽  
Enterohemorrhagic Escherichia Coli ◽  
Fecal Coliforms ◽  
Escherichia Coli O157 ◽  
Natural Background ◽  
Minimally Processed ◽  
E Coli

The ability of Listeria monocytogenes and Escherichia coli O157:H7 inoculated by immersion (at 4.6 and 5.5 log CFU/g, respectively) to survive on artichokes during various stages of preparation was determined. Peeling, cutting, and disinfecting operations (immersion in 50 ppm of a free chlorine solution at 4°C for 5 min) reduced populations of L. monocytogenes and E. coli O157:H7 by only 1.6 and 0.8 log units, respectively. An organic acid rinse (0.02% citric acid and 0.2% ascorbic acid) was more effective than a tap water rinse in removing these pathogens. Given the possibility of both pathogens being present on artichokes at the packaging stage, their behavior during the storage of minimally processed artichokes was investigated. For this purpose, batches of artichokes inoculated with L. monocytogenes or E. coli O157:H7 (at 5.5 and 5.2 log CFU/g, respectively) were packaged in P-Plus film bags and stored at 4°C for 16 days. During this period, the equilibrium atmosphere composition and natural background microflora (mesophiles, psychrotrophs, anaerobes, and fecal coliforms) were also analyzed. For the two studied pathogens, the inoculum did not have any effect on the final atmospheric composition (10% O2, 13% CO2) or on the survival of the natural background microflora of the artichokes. L. monocytogenes was able to survive during the entire storage period in the inoculated batches, while the E. coli O157:H7 level increased by 1.5 log units in the inoculated batch during the storage period. The modified atmosphere was unable to control the behavior of either pathogen.

Inhibition of Salmonella Typhimurium and Listeria monocytogenes in Mung Bean Sprouts by Chemical Treatment

2002 ◽  
Vol 65 (7) ◽  
pp. 1088-1092 ◽  
Author(s):  
SUN-YOUNG LEE ◽  
KYUNG-MI YUN ◽  
J. FELLMAN ◽  
DONG-HYUN KANG
Keyword(s):  
Lactic Acid ◽  
Listeria Monocytogenes ◽  
Salmonella Typhimurium ◽  
Sodium Hypochlorite ◽  
Mung Bean ◽  
Storage Period ◽  
Log Reduction ◽  
Mung Bean Sprouts ◽  
Chlorous Acid ◽  
Bean Sprouts

This study was undertaken to compare the efficacies of chlorous acid (268 ppm), sodium hypochlorite (200 ppm), and lactic acid (2%) in eliminating total mesophilic microorganisms, Salmonella Typhimurium, and Listeria monocytogenes on commercial mung bean sprouts immediately after treatment and during posttreatment refrigerated storage. Treatment with sodium hypochlorite for 10 min did not reduce the total aerobic count. However, treatment with lactic acid and chlorous acid for 10 min initially reduced the total aerobic count by 0.6 and 0.8 log CFU/g, respectively, and maintained the same level or a lower level of the total aerobic count during the storage time. Treatment with chlorous acid reduced Salmonella Typhimurium from 5.0 log to undetectable levels (<0.48 log CFU/g), and the pathogen remained undetectable over a 9-day storage period. Treatment with lactic acid resulted in an initial 3-log reduction and further reduced the number of Salmonella Typhimurium cells to undetectable levels after 3 days. For L. monocytogenes, treatment with chlorous acid resulted in an initial 5-log reduction, and treatment with lactic acid resulted in a 2-log reduction at the beginning and undetectable levels after 9 days. When chemically injured cells were investigated by the selective overlay method, no statistical difference was observed (P < 0.05) between the number of injured cells recovered following treatment with chlorous acid and the number of bacteria counted on selective media, whereas sodium hypochlorite generated more injured cells than the other treatments did. These data suggest that treatment with chlorous acid may be useful in reducing total mesophilic microorganisms, Salmonella Typhimurium, and L. monocytogenes in commercial mung bean sprouts.

Inhibition of Listeria monocytogenes by Bacteriocin-Producing Pediococcus During the Manufacture of Fermented Semidry Sausage1

1990 ◽  
Vol 53 (3) ◽  
pp. 194-197 ◽  
Author(s):  
ELAINE D. BERRY ◽  
MICHAEL B. LIEWEN ◽  
ROGER W. MANDIGO ◽  
ROBERT W. HUTKINS
Keyword(s):  
Listeria Monocytogenes ◽  
Acid Production ◽  
Initial Level ◽  
Bacteriocin Production ◽  
Heating Process ◽  
Internal Temperature ◽  
Carbohydrate Fermentation ◽  
Fermentation Period ◽  
And Storage

A bacteriocin-producing Pediococcus species inhibitory to Listeria monocytogenes was used to manufacture fermented semidry sausage. Separate 13.6 kg batches of a commercial summer sausage formulation were inoculated to contain an initial level of 106 cells/g of Listeria monocytogenes Scott A. In each of two independent studies, an ca. 2 log10 CFU/g reduction of L. monocytogenes occurred over the fermentation period, as compared to a less than 1 log10 CFU/g reduction in sausage fermented with a non-inhibitory Pediococcus strain. Inactivation of L. monocytogenes was also observed in one study where adequate acid production did not occur (pH>5.5), indicating that bacteriocin production occurred independently of carbohydrate fermentation. Following heating to an internal temperature of 64.4°C and storage up to 2 weeks, 9 of 90 sausages sampled were positive for Listeria. Recovery was intermittent and did not indicate that the bacteriocin was effective in eliminating L. monocytogenes that had survived the heating process.

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